2-((5&#39;-(3&#39; and/or 4&#39;-substituted)isoxazoyl) methylidene)-3,4,10-trioxo-1,2,3,4,4a,9,9a,10-octahydroanthracenes



United States Patent Office 3,502,660 Patented Mar. 24, 1970 US. Cl. 260240 14 Claims ABSTRACT OF THE DISCLOSURE A multi-route process for the synthesis of tetracylinetype antibiotics involving (1) the aldol condensation of a 3,4,10-trioxo-l,2,3,4,4a,9,9a,10-octahydroanthracene and a 3- and/or 4-substituted-5-formylisoxazole; (2) dehydration of the aldol condensation product to a 2-[(5'-(3'- and/ or 4'-substituted isoxazolyl) methylidene] -3 ,4,10-trioxo-1,2,3,4,4a,9,9a,IO-Octahydroanthracene; followed by (3) Michael addition of an amine to produce 2-[(5-(3- and/or 4'-substituted)isoxazolyl)substituted aminomethyl] 3,4,10 trioxo 1,2,3,4,4a,9,9a,10 octahydroanthrav cenes; (4) chemical or catalytic reduction of the [(isoxazolyl)aminomethyl] 3,4,10-trioxo-octahydroanthracenes to 3-hydroxy-4,10-dioxoand 4,10-dioxo derivatives, respectively; (5) cleavage of the isoxazole ring of the reduced compounds to the corresponding 4,10-dioxo-1,2,3, 4,4a,9,9a, 10 octahydroanthracene-Z- [oc- (amino acetonyla-llitlllfiS]; (6) followed by cyclization of 12a-deoxytetracycline or tetracycline derivatives; or, alternatively, (7) cyclization of [(isoxazolyl)aminomethyl] 4,10 dioxooctahydroanthracenes to naphthaceno(3,2 D)isoxazoles with subsequent cleavage of the isoxazole ring to produce l2a-deoxytetracyclines; and (8) 12a-hydroxylation to a tetracycline. The intermediate compounds of the process are limited to the following classes: 2-[5-(3' and/or 4' substituted)isoxazolyl)methylidene] 3,4,10-trioxo-1,2, 3,4,4a,9,9a,10 octahydroanthracenes; 2 [(5'-(3' and/or 4' substituted isoxazolyl)aminomethyl]-4,10-dioxo-1,2,3, 4,4a,9,9a,10-octahydroanthracenes, the 3-oxo, the 3-hydroxy, the 3-lower alkanoyloxy and the 3,4-cyclic carbonates thereof; 4,10-dioxo-1,2,3,4,4a,9,9a,10-octahydro anthracene 2 [ct-(amino)acetonyl-a-nitriles]; and naphthaceno (3,2-D)isoxazoles, all of which are useful as bactericides and/or chelating agents.

This application is a continuation-in-part of copending application Ser. No. 484,723, filed Sept. 2, 1965, now abandoned which in turn is a divisional application Ser. No. 209,268, filed July 11, 1962, now abandoned, said latter application being a continuation-in-part of application Ser. No. 133,011, filed Aug. 18, 1961, now abandoned.

This invention relates to a process of preparation of antibacterial agents. More particularly, it is concerned with the discovery of new and novel synthetic routes for the preparation of known as well as new tetracycline products. It is also concerned with the new and useful tetracycline products obtained thereby as well as with the new intermediates of the processes.

The tetracycline antibiotics comprise a group of biologically active hydronaphthacene derivatives having the following essential structural features. The number system indicated is that employed by Chemical Abstracts."

Among the biologically active members of this group are those containing the following substituent groups:

Substituents Common name 7 eye ne. 4-N(CH:):,6-CHa,12a-OH trdeoxytetracycline. 4-N(GH3);,12a-OH r fi deoxy-fi-demethyltetracycline. 442551-1 )z,6-OH,6-CH ,7-B1,123- 7-bromotetrjacycline.

4-N( H )1,6-OH,7-Ol,12a-0H 6-demethyl-7-chlorotetraeycline. 6-0 ,6-CHa,12a-0H 4-desdimethylaminotetraeycline. 6-QH,6-CH ,7-C1,12a-OH edesdimethylaminoJ-chloro- .2 tetracycline. 4-N(CH )z,6-OH,l2fl-OH fi-demethyltetracyeline. 12a-OH 6-deoxy-6-demethyl-4-desdlmethylaminotetracycline.

The present new processes utilize 3',4,10-trioxo-1,2,3,4,

4a ,9 ,9'a-,lo-octahydroanthracenes (Formula I) as starting materials to produce both known and new tetracyclines having the formulae A H NRaRt x I OH Xi OH,

CONHRs X I 2 d H (XXIV) A H NRQR X OH X. y

CONHRa (XXV) wherein the various terms are as defined below, by the reaction sequences illustrated in Flow Sheets I and II. It will be appreciated by those skilled in the art that several alternative routes exist for the conversion of compounds of Formula I to the final products of Formulae XXIV and XXV. The particular route adopted for the preparation of a given tetracycline is largely dependent upon economic factors, such as availability of materials, and yields of reaction products throughout the sequence.

Further, the conditions for any reaction in the sequence can, unless otherwise indicated, be varied Within the skill of the art. The actual conditions employed are determined by the above listed factors as well as by type and availability of equipment.

FLO? SHEET I 1} NR-gR OH OH CONHRs B 3 8 (XXIV) A NR3R4 X I 0 X1 1 IL, x I Y a I 6 a (XIX) when Y: is l 002R and Y; is H l FLOW SHEET I-Continued In the compounds of this sequence, X is selected from the group consisting of hydrogen, hydroxy, trifluoromethyl, amino, mono and di-lower alkylamino, alkanoylamino containing 2 to 4 carbon atoms, lower alkyl, alkanoyloxy containing 2 to 4 carbon atoms; and OR wherein R is selected from the group consisting of lower alkyl and benzyl;

X is selected from the group consisting of hydrogen, chloro, lower alkyl and trifluoromethyl;

X is selected from the group consisting of hydrogen, hydroxy, and OR in which R is as previously defined;

A is selected from the group consisting of hydrogen, lower alkyl, and B OCH(B wherein B is lower alkyl and B is selected from the group consisting of hydrogen and lower alkyl;

R and R when taken together with the nitrogen atom to which they are attached form a nitrogen heterocyclic ring selected from the group consisting of piperazyl, N-(lower alkyl)piperazyl, piperidyl and morpholinyl;

R is selected from the group consisting of hydrogen, alkanoyl containing 1 to 4 carbon atoms, and methyl;

R is selected from the group consisting of alkyl containing 1 to 4 carbon atoms;

R is selected from the group consisting of hydrogen and lower alkyl;

Y is selected from the group consisting of hydrogen, formyloxy and lower carbalkoxy;

Y is selected from the group consisting of hydrogen, carbobenzoxy, carboxy, lower carbalkoxy, and

CONH CH Y is selected from the group consisting of lower carbalkoxy, carbobenzoxy, carboxy, CONH and CONH (CH and, when Y is hydrogen, CON(CH It should be noted that although the X, X and X terms in the benzenoid moiety of the above generic structures appear in the same sequence, they need not be present in this sequence in actual practice. This representation is for convenience only and is not to be taken to indicate, for example, that X always represents the S-substituent, or that X represents the 6- or the 7-substituent. They can occur in any sequence in the benzenoid moiety.

A wide variety of 4-aminotetracyclines are, of course, prepared according to the present processes by substituting various primary or secondary alkyl amines for dimethylamine. Suitable amines include other dialkylamines, e.g. methyl, ethyl, propyl, etc. amines; heterocyclic amines, e.g. pyrrolidine, morpholine, and ammonia.

Of the present new compounds of particular value are those containing the following benzenoid moiety;

(XXIV) (XXIII) in which X, X and OR are as described above since these compounds are suitable for the preparation of known tetracycline compounds, i.e., and in addition, new and useful tetracycline compounds not previously described.

In the above sequence of reactions many of the indicated steps are carried out by standard procedures known to those in the art, e.g., hydrolysis, esterification, acylation, reduction, ring closure, Mannich reaction, Michael additron, etc.

The above sequences of reaction may be summarized as follows: From I to XVI is an aldol condensation (fol lowed by dehydration) with a 5-formyl isoxazole, generally a lower carbalkoxy derivative. The reaction is catalyzed by acids or metals, e.g. metal salts, such as magnesium chloride in acetic acid, and preferably by metal alkoxides. It is advantageously conducted in an inert atmosphere, e.g. nitrogen, at a temperature of from about -120 C. for from M; to about 24 hours.

The acid catalyzed condensation is conveniently carried out in glacial acetic acid as solvent. Non-hydroxylic solvents such as benzene, Xylene, toluene, dioxane, dimethoxyethane, diethyleneglycoldimethyleter and dimethylformamide are useful solvents for the metal catalyzed condensation, especially when using metal alkoxides. Magnesium methoxide and aluminum t-butoxide are especially useful in this condensation. Of course, when active hydrogen is present in the reactant, one extra equivalent of the alkoxide is used per active hydrogen. The a-hydroxy ester, wherein the elements of water are added to the unsaturated ester, may also be obtained in small yield. Its production is favored by short reaction periods and low temperatures. Dehydrating agents, such as p-toluenesulfonic acid in benzene permit dehydration and regeneration of the unsaturation.

The conversion of XVI to XVII is a Michael reaction with an amine HNR R The reaction is conducted at a temperature of from about 70 C. to about 10 C. preferably in the lower temperature range e.g. below 50. An excess of the amine is employed; a sufiiciently large excess frequently being used to serve both as solvent and as reactant. A variety of other solvents can be used and are actually necessary when the amine is a solid at the temperature of the reaction. Such solvents include tetrahydrofuran, ethylene glycol ethers, diethyleneglycol ethers and chloroform. The only criteria essential for the solvent are adequate solubility for the reactants, inertness and a sufficiently low freezing point.

The reaction is run for periods of from 15 minutes to 24 hours depending upon the reactants and temperature employed. Oxyben should be excluded during the period when the product is in contact with the excess amine. The order of addition of the reactants appears in general, to be immaterial to the outcome of the reaction.

The products are unstable unless kept cold; that is, below 0 C., and desirably at or below 15 C. In spite of their thermal instability they can, if desired, be isolated by working up the reaction mixtures at low temperatures, e.g., in a cold box. The products must, of course, be stored at a low temperature. Ho qvever, they need not be isolated for utilization in the hereindescribed reaction sequences.

From XVII to XVIIa is a selective reduction with a suitable chemical reducing agent, such as metal hydrides, especially sodium borohydride. The reaction is carried out by dissolving the Mannich base in a suitable reactioninert solvent such as 1,2-dimethoxyethane, ethyleneglycol ethers, diethyleneglycol ethers and liquid amines. Reaction periods of from about 10 minutes to about 24 hours are required. Of course, when active hydrogen is present in the reactants in addition to the fl-diketone system, one additional equivalent of sodium borohydride is required per active hydrogen.

The reduction is advantageously conducted by adding the sodium borohydride all at once to a vigorously stirred solution of the Mannich base (XVII) in one of the aforementioned solvents at 70 C. followed by gradual increase in the temperature to C. In this process, as above, 0.25 to 6.0 moles of reducing agent per mole of Mannich base is used. As much as 20 moles of reducing,

agent may be used. A ratio of 4-6 is, however, preferred. In the case of liquid amine solvents, the reduction is most conveniently conducted by addition of the sodium borohydride to the reaction mixture obtained in the conversion of XVI-XVII. j

From XVI to XVIIa is a selective reduction with a suitable chemical reducing agent, such as sodium borohydride, of the Mannich reaction product XVII. It is represented as a one-step conversion since the Michael reaction product need not be separated prior to reduction.

The Michael addition reaction with an amine HNR R as applied in the above steps wherein the Y and/or Y substituents of the isoxazolyl moiety of compounds of Formula XVI are lower carbalkoxy concomitantly ef= fects, to some extent at least, conversion of the lower carbalkoxy group(s) to an amide CONR R While conversion of the lower carbalkoxy group(s) to amide appears to be the predominating reaction, except where R and R are both alkyl, the presence of unchanged lower carbalkoxy groups is detectable by such means as infrared spectroscopy. When Y is hydrogen, substantial conversion of Y (lower carbalkoxy) to an amide occurs even when R, and R are both alkyl.

The lower carbalkoxy groups, Y and Y of compounds of Formula XVI are readily converted to amide groups (CONR R by treatment of the isoxazolyl esters, or a metal chelate thereof, e.g., aluminum chelates, with the desired amine at low temperatures. The thermal instability of the amine addition products of Formula XVII permits their facile conversion to ;the isoxazolyl amides of Formula XVI by removal of the NR R groups via heating in vacuo.

The thus produced isoxazolyl amides of Formula XVI (Y and/or Y =CONR R are then subjected to the Michael addition reaction with the same or a different amine to give products of Formulae XVII and XVIIa.

The addition of secondary amines may be facilitated by first converting the ester functions (Y Y to amides with primary amines. It appears that in the conversion of the unsaturated tricyclic triketone V isoxazolyl amides (XVI) to the amine addition products (XVII) the equilibrium is shifted in favor of the amine addition product by the presence of amide functions, possibly because of the low solubility of the products in the reaction medium.

The amide groups of structures XVI, XVII, XVIIa and other structures in the sequences of Flow Sheets I and II can, if desired, be converted to ester groups by refluxing in concentrated hydrochloric acid followed by re-esterification of the acid. In general, it is preferred to employ the isoxazolyl esters rather than the amides in the reaction sequences of Flow Sheets I and II. Diamides are converted to their half-lower carbalkoxy esters in this manner. Mono-amides can, of course, be transformed to esters by this process.

XVIia XXVI-Formation of the cyclic carbonate at the 3,4-positions of the octahydroanthracene moiety by reaction with phosgene or preferably ethyl chlorocarbonate, or other alkyl chlorocarbonate, or carbonyldiimidazole in the presence 7 of pyridine or triethylamine or 1,4- diaza[2,2,2]bicyclooctane. The reaction is conducted at a temperature of from about -10 C. to about 10 C. in reaction-inert solvents such as acetonitrile, dioxane, chloroform, benzene, toluene, and ethers of ethyleneand diethylene-gl ycol for periods cIf from about 5 minutes to 24 hours. The phosgene or alkyl chlorocarbonate is generally mixed with the base and added to the octahydroanthracene reactant. Alternatively, the base and octahydroanthracene moiety are mixed together and the phosgene or alkyl chlorocarbonate added thereto. The base may be present in amounts ranging from one equivalent to a large excess. However, 2-3 equivalents is preferred.

The cyclic carbonate is then cyclized to the fused isoxazole structure and the cyclic carbonate hydrolyzed under mild acid conditions".

Tlie cyclic carbonate intermediates afford a particularly advantageous avenue for, the utilization of the tricyclic triketones (I) in the synthesis of tetracyclines since they direct the ring closure reaction in a stereo-specific manner to provide the desired configuration of the 12a-hydroxy group. This represents a simplification over the other routes exemplified in Flow Sheets I and II wherein a hydroxy group is removed then reintroduced at the 12aposition at a late stage in the sequence; I

The cyclization reaction is carried out using l-3 equivalents of a basic condensing agent, such as sodium hy= dride, sodium alkoxides, sodium amide and magnesium alkoxides, a reaction-inert solvent diethyleneglycol dimethyl ether, toluene, anisole, benzene, dimethyl sulfoxide, dimethylformamide, dimethoxyethane, and in the case of sodium amide, liquid ammonia. Temperatures of up to 100 C. may be used in solvents of appropriate boiling point. However, temperatures below about C. are generally preferred, for reaction periods of from 0.5 hour to 24 hours. i

" XVIIa XVIIIConversion to the diketone compound is accomplished by reaction with acetoformic anhydride according to known procedures followed by removal of the 3-formyloxy group generally by treatment with finely divided zinc metal in an organic acid (e.g. formic acid) or with zinc dust in an organic acid in the presence of a metal which forms aehelate with the substrate (zinc chloride in acetic acid). A diluent such as methanol may be employed. Alternatively, zinc chloride in acetic acid, catalytic hydrogenation (5% Pd-C) in tetrahydrofuran or formic acid at elevated pressures is .used. Care must be taken to avoid overreductiou, that is reduction of the 4,10-keto group. For this reason mild conditions are required. When using zinc dust-formic acid, for example, reaction is elfected at room temperature with contact times of brief duration.

XVII- XVIIIReduction of the 3-oxo function of the starting compound which may be carried out by standard methods, e.g., catalytic hydrogenation at low temperatures in ethyl acetate (e.g. C.) over palladium to produce the corresponding alcohol which is, as the free alcohol or ester, e.g. acetate, susceptible to further reduction at low temperatures by either catalytic or chemical means, e.g. zinc in acetic or formic acid.

XVIII? XIXRing closure of compounds in which Y "is carbalkoxy is conducted in the presence of a base, for

example, sodium hydride. Generally speaking, the ring closure is accomplished under conditions similar to those described above under the cyclic carbonate cyclization. However, somewhat more vigorous conditions may be necessary to form the requisite dianion of the B-diketone system. This may be generally recognized by a color change to a deep reddish color. When using sodium hydride and dimethylformamide, this change occurs, for

the most part, upon heating to approximately 80 C. Prolonged reaction times of several days at room temperature also effect the reaction.

Where Y is a carboxamide function, a modified ring closure reaction sequence is utilized. Compounds of Formula XVIII are treated with 2-3 moles of a trialkyl oxonium salt, such as trimethyl-oxonium fluoborate or trial-kyl-oxonium fluoborate (for other such salts see Meerwein et al., Ber. 89, 20602079 (1956)) in a solvent (chloroform, methylene chloride, tetrachloroethane) at about 4070 C. for from about 6 to about 48 hours under dry nitrogen. (The reaction temperature is, of course, conditioned by the boiling point of the solvent used.) Following this, 3-6 equivalents of sodium hydride is added and the mixture refluxed for from about 5 minutes to one hour after which an additional 2-3 equivalents of sodium hydride followed by 1-3 equivalents of methanol is added. The vigorous exothermic reaction, the cyclization stage, which usually occurs is complete in from 5 to 15 minutes. The crude reaction products appear to be enol ethers which are readily hydrolyzed by gentle warming with dilute acid to the fused isoxazoles of Formula XIX.-

XIX XXMethods for cleavage of the isoxazole ring vary depending upon the nature of the Y substituent. When Y is carbalkoxy standard alkaline hydrolysis of XIX in the form of a metal chelate of an alkaline earth metal or heavy metal such as calcium, magnesium, cadmium, copper, nickel, and preferably zinc, using alkali or alkaline earth metal hydroxides, or acid hydrolysis using mineral acids is employed. Temperatures of from 30 to 100 C. for periods of about 0.5 hour to 12 hours are operative when using 0.5% to 5% of alkaline or acid hydrolyzing agent.

In the case of alkaline hydrolysis cleavage of the isoxazole ring follows conversion to the carboxyl-ate anion. In the case of acid hydrolysis it is usually necessary to convert the acid to an alkali or alkaline earth metal salt and warm to 5080 C. to effect decarboxylation and cleavage. Treatment With aqueous ammonia in the presence of copper powder also cleaves an ester or acid isoxazole derivative.

When Y is carboxamido or mono-substituted carboxamido treatment with at least 2 equivalents of sodium hydride or other strong base, e.g. sodium or lithium amide, at 80-110 C. in a reaction-inert solvent, dimethyl sulfoXide, dimethylformamide, ethyleneand diethylene-glycol ethers, for from 5 minutes to one hour is used.

XXV I- XXIV and XX XXIIIConversion of the 2- cyano group to a carboxamido group by the method described in United States Patent 3,029,284, issued Apr. 10, 1962, wherein is described the conversion of tetracycline nitriles to the corresponding N-alkylated carboxamide (e.g. t-butyl, isopropyl) by the Ritter Reaction followed by dealkylation of the resulting N-alkylated carboxamide with concentrated mineral acid and water. An alternate method of converting the nitrile to the amide is by hydration wih mineral acid such as sulfuric or 48% hydrobromic acid preferably at elevated temperatures, e.g. between 50 and 100 C., for from 530 minutes or with excess polyphosphoric acid at room temperature for prolonger reaction periods such as 12 to 24 hours. Still another method, especially applicable to the preparation of acid stable tetracyclines from the corresponding nitriles, involves reaction of said nitriles with hydrogen fluoride or boron trifluoride complexes in an aqueous medium at a temperature of from 0100 C. as is described in Us. Patent 3,069,467, issued Dec. 18, 1962.

XXI XX and XXI XXII represent ring closure by base catalyzed acylation using, for example, sodamide, sodium triphenyl methyl, potassium amide, alkali metal alkoxides or preferably sodium hydride. This is essentially a reaction of the type described by Hauser and 10 Harris, I. Am. Chem. Soc. 80, 6360 (1958) who described acylation reactions of dianions derived from fi-diketones.

A ratio of at least 4 equivalents of base and desirably a great excess of up to 10 equivalents is employed. A variety of reaction-inert solvents can be used, e.g. benzene, xylene, toluene, anisole, dimethylformamide and, in the case of alkali metal amides, liquid ammonia. Dimethylformamide containing a small amount of methanol is the preferred solvent. Reaction is conducted under nitrogen at a temperature of from about to about 150 C., preferably C., for periods of from about 3 minutes to up to 24 hours depending upon the reactants. A period of 5-7 minutes is adequate, indeed preferred, in most instances.

XXV-- XXVIThis cyclization is advantageously conducted by first converting the hydroxy ketones (structure XXV compounds) to their acetates, forrnates or the cyclic carbonates. The cyclizing procedure is the same as that described above in connection with the isoxazole cyclic carbonate except that one extra equivalent of sodium hydride is used.

It is noted that in compounds of Formula XXV wherein Y is a carboxamide function, e.g. CONH(CH reaction leading to formation of the cyclic carbonate of the hydroxy ketone also causes cyclization of the side chain:

o 0 t w For convenience, these compounds are designated herein as 2,3-tetracycline-4,5'-isoxazole derivatives with the 1,2 and 3-isoxazole positions designated as 1, 2' and 3'. This permits the use of the tetracycline numbering of the ring positions. For example, 1,11,12-trioxo-l0-hydroxy-4-dimethylamino 1,4,4a,5,5a,6,11,11a,12,12a decahydronaphthaceno (3,2-D)isoxazole-3-carboxylic acid ethyl ester is conveniently designated as ethyl 6,12a-dideoxy-6- demethyl-2,3-tetracycline-4',5'-isoxazole-3' carboxylate.

XVIII- XXI and XVIIa XXVCleavage of the isoxazole ring by aforementioned procedures. XX- QVI and XXIII- XXIV-12a-hydroxylation.

The compounds of structure XXIII and XXIV are biologically active tetracycline products, the latter being 12adeoxytetracyclines which are converted to tetracycline compounds XXIV by introduction of a 12a-hydroXy group by known procedures such as described in the J. Am. Chem. Soc., 81, 4748 (1959).

A preferred method of 12a4hydroxylation is the method described in U. S. Patent 3,188,348, issued June 8, 1965, wherein is described the hydroxylation of certain metal chelates of the 12a-deoxytetracyclines. The advantage of this latter process lies in the fact that the hydroxy group is introduced cisto the hydrogen at position 4a.

The ring closure reactions are carried out by the general methods as hereinafter described.

The requisite isoxazole-S-aldehydes having the formula wherein Y.;, is selected from the group consisting of hydrogen, cyano, CONH carboxy, carbobenzoxy and lower carbalkoxy; and Y is selected from the group consisting of cyano, carboxy, CONH carbobenzoxy and lower carbalkoxy, can be prepared by any one of several methods. For example, ozonolysis of the corresponding 5-styryl isoxazole obtained by the known procedure (JCS. 3663, 1956) which comprises reaction of the appropriate 2,4-diketo-6-phenyl-hex-S-enoic acid derivative (C H -CH=CH-COCH CO-CO Y) with hydroxylamine.

3,4-dicarbalkoxy-S-formylisoxazoles are obtained by the reaction of the desired alkyl-yq-dialkoxyacetoacetate with ethyl-a-chloro-a-oximinoacetate in the presence of a base, e.g. sodium hydride, followed by cyclization of the thus roduced oxime of ethyl-a,'y-diketo-fl-carbethoxy-6,6-dialkoxy valerate by treatment with p-toluene sulfonic acid or other suitable dehydrating agent in a non-polar solvent, e.g., benzene, for from 15 minutes to 24 hours at 30 C. and preferably at room temperature, with continuous removal of Water. The acetal of -formyl-3,4-dicarbalkoxyisoxazole is converted to the 5-formyl derivative by acid hydrolysis.

Alternatively, isoxazoles are prepared by the reaction of an enamine of alkyl-' ,'y-dialkoxy acetoacetate with achloroximino acetate.

By ester interchange other alkyl groups or the benzyl group are conveniently introduced into Y or Y; and Y The carbobenzoxy derivatives are of value since they afford easy access to the corresponding carboxy acids by catalytic hydrogenolysis. Further, the esters can be converted to amides and thence to nitriles by reaction with ammonia followed by dehydration of the amide with, for example, benzenesulfonyl chloride.

Utilization of a 'y,' -dialkoxyaceto acetamide in lieu of an alkyl-' -dialkoxyacetoacetate in the above described reaction with ethyl a-chloro-a-oximinoacetate produces the corresponding acetal of 3-carbethoxy-4-carboXamido-5- formylisoxazole. Acid hydrolysis of the acetal by HCl or preferably 48% HBr for about 10 minutes at room temperature yields the 5-formyl derivative.

When the substituents of the present compounds are hydroxy or amino, the use of a blocking group is sometimes advantageous in obtaining high yields during their preparation. Especially useful blocking groups are acyl, benzyl, tetrahydropyranyl, methoxymethyl, methyl and ethyl radicals. Benzyl ethers are particularly easily reduced to hydroxyl groups. Tetrahydropyranyl ethers are easily removed under mildly acidic conditions. Acyl groups which may be used include the acetyl, propionyl and butyryl, as well as the benzoyl, succinyl, phthaloyl, and the like. The lower alkyl blocking groups are preferred since these compounds are readily preparable.

In the octahydroanthracene compounds in which the 4a-substituent (lla-substituent in tetracycline compounds) is hydrogen, the reactive 4,10fl-diketone system (11,125- diketone system of tetracycline compounds) may be blocked by formation of derivatives of said system, e.g., 4-enol derivatives. It is understood, of course, that enol formation may occur at the 10-position but for the sake of convenience such derivatives will be designated herein as 4-enol derivatives. The enol methyl ethers are prepared by reaction with excess diazomethane in methanol solution at room temperature. Such reactions usually require several days for completion.

The enol radicals are hydrolyzed by treatment with aqueous acid as is well known by those skilled in the art. When the ether radical is benzyl, hydrogenolysis over a noble metal catalyst may also be used.

The new compounds described herein are useful as chelating, complexing or sequestering agents. The complexes formed with polyvalent metal ions are particularly stable and usually quite soluble in variou organic solvents. These properties, of course, render them useful for a variety of purposes wherein metal ion contamination presents a problem; e.g. stabilizers in various organic systems, biological experimentation, metal extraction. They are further useful in analysis of polyvalent metal ions which may be complexed or extracted by these materials and as metal carriers. Other uses common to sequestering agents are also apparent for these compounds.

In addition, the compounds of Flow Sheets 1 and II are especially valuable as intermediates in chemical synthesis particularly in the synthesis of fi-deoxytetracycline, 6-deoxy-fi-dimethyltetraeycline and other novel antimicrobial agents bearing structural similarities to the tetracycline antibiotics. Many of the herein described compounds, especially those containing one or more hydroxy groups in the benzenoid moiety, are useful as antibacterial agents in their own right.

In the present new process, particularly as applied to the synthesis of known-tetracyclines, it i preferred to employ intermediates in which the hydrogen atoms at the 9a and 2-positions of the anthracene ring (corresponding to the 4a and Sa-positions of the tetracycline nucleus) are in the cis arrangement. For example, preferred compounds are depicted by the following formula (syn. compounds) in which G is a substituent other than hydrogen, as contrasted with anticompounds of the formula:

In general, syn and anti compounds are separable by virtue of differences in physical properties, e.g., differences in solubility in various solvents. Usually, fractional crystallization or adsorption chromotography permits ready separation. Both the syn and anti compounds are diastereoisomers.

It is a particular advantage of the novel triketo octahydroanthracenes of the present invention that, by virtue of the activating influence of the keto oxygen at C-3, they equilibrate to the predominately cis configuration in the course of preparation. This enables the synthesis to proceed in stereo specific fashion without the loss of material that would otherwise be entailed in the separation of syn and anti compounds.

However, since in the production of compounds of this type, the product may consist of a mixture comprised of compounds diifering in position 2 of the anthracene nucleus, i.e. the hydrogen being both cis and trans to the hydrogen at position 9a, the mixture can be converted to the predominately cis arrangement by equilibration using extended periods for the amine additions reaction.

It is recognized by those in the art that, when such compounds have an asymmetric center in the substituent G, they exist as two diastereoisomers which, as previously mentioned, may be separated by fractional crystallization for each of the syn and anti compounds. Of course, as is known, diastereoisomers are racemic modifications consisting of two structures which are mirror images (optical antipodes). The racemic modifications may be resolved according to standard procedures. In the present process it is preferred, however, to utilize the diastereoisomers of the syn compounds since changes in configuration may occur during the various procedural steps of the total synthesis to tetracycline compounds, thus necessitating costly and time-consuming resolution procedures. The syn diastereoisomers are converted to tetracycline products which consist of the normal tetracyclines and their 4-epimers which are separable by known procedures. of course, the 4-epitetracyclines are useful in that they are converted to normal tetracyclines by known procedures.

The starting compounds of structure I are prepared according to the following procedure:

A\ B A B x -oom corn X1 X1 X2 C R5 X2 I I(/ where R5=OH where R5=0R1 A B A B x X COzH 002m Xi X1 C 0 2R1 O X2 15 X2 I I A B X In the above formulae, X, X X and A are as previously described with the exception that substituent X is preferably not a nitro group since this group deactivates the ring of compounds of structure II in the ring closure reaction to those of structure III (R is lower alkyl or benzyl) and R is hydroxyl, benzyloxy, lower alkoxy or halogen (Cl, F, Br, or I). Alternatively, the corresponding nitriles (e.g. where COR is replaced by CN) may be used. Further, at least one of the two positions of the benzenoid ring ortho to the diester side chain must be available for the ring closure of structure III compounds. If desired, halogen (C1 or Br), may be introduced into compounds of structure I, II, III and IV in which at least one of the benzenoid substituents is hydrogen by direct halogenation with a chlorinating or brominating agent by methods generally employed for halogenation of an aromatic ring. A variety of such agents are known to those in the art and include phosphorus pentachloride and pentabromide, sulfuryl chloride, N-chloro or bromoalkanoamides, e.g. N chlorand N bromacetamide; N-chloro (or bromo) alkanedioic acid imides, e.g. N-halosuccinimide; N-halophthalimide; chlorine; bromine; N- haloacylanilides, e.g. N-bromoacetanilide, propionilide and the like; 3-chloro-, 3-bromo, 3,5-dichloro and 3,5-dibromo-5,5-dimethylhydantoin, pyridinium perbromide and perchloride hydrohalides, e.g. pyridinium perbromide hydrobromide; and lower alkyl hypochlorites, e.g. tertiary butylhypochlorite.

The ring closure of compound II to III is accomplished by any of the commonly employed methods for such reactions which generally involve the use of a dehydrating or dehyrohalogenating cyclization agent. With compounds of structure II, a preferred method when R is OH or alkoxy involves treatment of the starting compound with such ring closure agents as hydrogen fluoride or polyphosphoric acid. When R in the starting compound is hydroxyl it is usually preferred to use hydrogen fluoride; when R is lower alkoxy, polyphosphoric acid. When R is halogen, a Friedel-Crafts catalyst, of course, should be employed, e.g. aluminum chloride. m-Hydroxyor alkoxy-benzyl compounds of structure II having CN in place of COR lend themselves to the Hoesch synthesis (.Beriohte, 48, 1122 and 50, 462) wherein treatment with dry hydrogen chloride in the presence of zinc chloride leads to imine formation, and hydrolysis of the latter provides the tetralone keto group.

The condensation of compounds II or III in which R is 'OR, with oxalic ester as well as ring closure of compounds IIIa (after esterificati-on of the free acid with R OH) are effected by the general methods for ester condensation reactions of this type. Usually the reaction is carried out in the presence of a strong base such as alkali metal, alkali metal alkoxides and hydrides, sodamide and the like. If the star-ting compound in the oxalate condensation contains free hydroxyl or amino groups, it is preferred to block such groups by alkylation or acylation by known procedure-s. After the reaction is completed, the blocking groups may be removed, if desired. The resulting product from structure II, i.e. the corresponding Z-carbalkoxy or carbobenzyloxy compound of structure IV, on hydrolysis and decarboxylation yields compounds of structure I. Cleavage of the ether linkage or other blocking groups by any of the general methods, e.g. treatment with mineral acid such as concentrated hydrobromic or hydriodic acid, or when R is henzyl, hydrogenolysis, gives free hydroxy groups in the benzenoid portion.

The starting compounds of the above described processes, i.e. compounds of structure II are prepared by the following sequence of reactions: 7

j i ii V/\ COZRI X i5 X2K/ n coin,

x1 I i In the above sequence, R is lower alkyl or benzyl; and B is hydrogen or hydroxy. j,

FLOW SHEET m The first of these reactions for the preparation of compounds of structure VII is by means of Friedel-Qrafts reaction, e.g. AlCl in carbon disulfide. The conversion of compounds of structure VII to those of VIII in which A and B are hydrogen is by' catalytic reduction, e.g. over copper chromium oxide or noble metal, e.-g. palladium, catalyst' at from' atmospheric to superatmosphenc pressures of hydrogen gas; where A is alkyl and B hydroxyl, by reaction with a suitable Grignard reagent, e.-g AMg Halogen; where A is alkyl or hydrogen and B 1s hydrogen, by reduction, i.e. hydragenolysis, of corresponding compounds in which B is hydroxyl.

From VIII to IX is a standard ether hydrolysis, e.g. concentrated flaydrobrornic acid.

From IX to XI is an oxidation reaction (ozonolysis or hydrogen peroxide) giving rise to the dienedioic acid which on hydrogenation over a noble metal catalyst, e.g., palladium, palladium on carbon, platinum oxide, etc., gives compounds of structure II. In the ozonolysis reactions to form compounds of structureXI it is not possibie to employ as starting compounds those of structure IX in which there are adjacent hydroxyl groups in the benzene ring containing X, X and X as substituents, since such structures are susceptible to the oxidation reaction. 5 Further, in the ozonolysis reaction compounds of structure IX in which X, X and X are adjacent ether groups or adjacent ether and hydroxy groups cannot be used since they, too, are susceptable of oxidation. The ozonolysis reaction is applicable to compounds of structure VIII, subject of course, to the above limitation, wherein 0R represent an ether group. In such'cases the ester (XI) is obtained. In the hydrogenation reaction, compounds of structure XI may be used as the free acids or corresponding benzyl or lower alkyl esters to provide corresponding products of structure II. Of course, benzyl esters may undergo hydrogenolysis to the free acid.

In addition, appropriate methods are available for reduction of the benzoyl keto group to a secondary alcohol. For example, 11a and VII can be reduced with sodium borohydride, or by hydrogenation with alladium catalyst in non-acidic media. By other well-known replacement. procedures such as the following, the secondary alcohol may be converted to a readily replaceable sulfonic ester group, e.g. the tosylate, mesyla-te, etc., followed by reaction with an amine, a malonic ester, or the like, thus afiording means for introduction of an aminoor -CH(CO B group in the 6-position of the final tetracycline. In this sequence of reactions, when X and/or X are halogen, care should be taken to avoid prolonged hydrogenations which may result in the removal of the halogen atom. The possibility of halogen removal may be minimized by the use of a lower alkanoic acid, e.g. acetic or propionic as solvent for the reaction. Of course, if removed, halogen may be reintroduced if desired by the method hereinb efore described. e i

In these compounds of structure IX in which there are amino or adjacent hydroxy groups in the benzenoid moiety, such groups must be protected by suitable blocking groups, e.g. amino groups acylated; hydroxy groups etherified with lower alkyl or benzyl groups. Of course, the etherifying radical of the hyd-roxy group may differ from that represented by R. If the etherifying radical is benzyl it may subsequently be removed by hydrogenolysis. Alternatively, all ether groups can be removed *by hydrogen iodide treatment.

As will be appreciated irom the preceding reaction sequence it is m'ost'eonvenient to introduce the benzenoid substituents, X, X 'and X 'by employing the appropriate substituted benzoic acid derivative as starting material. Many of these benzoic acid derivatives are commercially available, and others may be readily obtained by those skilled in the art. W

B will be noted that a number of the later steps of the preceding sequences involve reaction conditions which may affect certain of the substituent groups signified by X, X and X For instance, in catalytic hydrogenation,

erg. V I I- VIII, halo groups are subject to hydrogenolysis and nitro groups are subject to reduction to amino; Therefore, where holo or nit'ro groups are desired in the final product, theseare best introduced subsequent to: the hydrogenation by an appropriate substitution reaction. In the case of ni-tro groups, these are preferably introduced subsequent to ring closure [II- 111] since the nitro group is a deactivating group for aromatic substitution and may cause difiicuity in effecting cyclization. When an aromatic amino group is present, it may be replaced by nitro by standard diazotization procedures followed by Sandmeyer reaction. This is most conveniently carried out on compound XVIII (Flo-w Sheet I) preferably as the enol ether or a later stage in the synthetic sequence. If the nitro group is present in the starting benzoyl suocinate XIII and is reduced during the course of the process to an amino group, the later may subsequently be alkyla-ted or acylated in conventional fashion to provide desirable products.

If the aromatic ring carries an acetylamino group, the latter will be hydrolyzed, e.g. in the reaction VIII IX, and subsequent reacylation is called for.

On commencing the sequence with a substituted benzoyl succinate, it is essential that an ortho ring position be unsubstituted, since cyclization to form the center ring of the hydroanthracene occurs at this position. For the preparation of the preferred compounds of structure I, which bear an OR substituent in the -position, the position of the benzene ring between the OR group and the keto group in the starting benzoyl succinate should be unsubstituted, to provide for the subsequent ring closure. On the other hand, it is preferred to have a substituent in what corresponds to the 8-position of compound I, since this precludes cyclization to that position in competition with the desired cyclization [II- 111]. An alkoxy, alkyl, or acylamino group can be conveniently carried in this position from the outset. Alternatively, an 8-substituent may be introduced during the reaction sequence, prior to the cyclization. For example, compound II may be halogenated at this position, e.g., by treatment with chlorine in the presence of a catalytic amount of iodine or ferric chloride.

Compounds of structure II are also prepared by the following sequences of reactions.

XII

CO2R1 X XIV The conversion of compounds of Formula XII to those of XIII is a Claisen-type condensation of the lower alkyl ester of XII with succinic acid diesters to provide Formula XIII compounds. The conversion of compounds of Formula XII to XIV is similarly a Claisen condensation using acetic acid esters. The conversion of compounds of Formula XIV to XIII is by alkylation reaction with a monohaloacetic acid ester, and the conversion of XV to 11a is such an alkylation followed by hydrolysis and decarboxylation. The preparation of compounds of Formula XV from those of Formula XIV is by standard alkylation procedures preferably using or corresponding nitrile. The conversion may also be effected by alkylation with a fi-halo acid derivative halogen-CH CH CO R or the corresponding nitrile. Each of these reactions are elfected under standard conditions known to those skilled in the art, e.g. in a reaction-inert solvent in the presence of a base such as Triton B (benzyltrimethylammonium hydroxide), sodamide, sodium hydride and their obvious equivalents.

The conversion of compounds of Formula XIII to those of 11a is by known standard reactions, e.g. by reaction of Formula XIII compounds with corresponding acrylic acid esters of the formula H C=CH CO R in which R is as previously described under the conditions of the Michael reaction. It may also be effected by alkylation with ,B-halo-alkanoic acids of the formula Halogen-CH CH CO R or of the corresponding nitriles. Hydrolysis and decarboxylation of these compounds gives structure Ila compounds. The conversion of structure IIa compounds to those of structure II is brought about by reactions as previously described for preparing structure VIII compounds.

The present invention additionally is adaptable for the preparation of other tetracycline molecules, as follows.

For compounds in which substituent X is nitro, the tetralone of structure II is nitrated by standard procedures, e.g., such as nitric-acetic anhydride-acetic acid mixtures or nitric acid-sulfuric acid mixtures. Those in which X is halogen, nitro or other such groups, are prepared by a Sandmeyer reaction of the corresponding diazonium salt with suitable salt reagents (Cu Cl Cu Br KI, etc.). The diazonium salt is obtained by diazotization of the amino compound, prepared from compounds of structure II in which X is amino or produced by the reduction of the corresponding nitro compound by conventional means, e.g., chemical means, such as, active metals (Sn) and mineral acids (HCl) or by catalytic hydrogenation, e.g., nickel catalyst and superatmospheric pressure.

The amino group may also be introduced in the benzenoid ring by coupling of aryldiazonium salts, e.g., benzene diazonium chloride or the diazonium salt of p-aminobenzenesulfonic acid, with compounds of structure II or III containing a free hydroxy substituent in the 5-position of the 4-tetralone ring (Ii-position of the benzene ring) followed by reduction of the resulting phenylazo compound, e.g., catalytic reduction over noble metal catalysts. An amino group may also be introduced in place of the keto carbonyl oxygen of compounds of structure VII and XV by reduction of the corresponding oxime or hydrazone, by reductive ammonolysis of the keto carbonyl group over noble metal catalysts or by reduction of the keto group to a secondary hydroxy group by sodium borohydride followed by conversion to the tosylate and replacement of the tosylate group by an amino group. The benzoyl keto group of compounds of structure IIa may be subjected to the Wittig reaction 19 as described in Angewandte Chernie 71, 260-273 (1959) to produce the alkylidene derivatives I10.

B20 C (B X COZRI C 2 1 ,2 X2 C z i X C 02R1 He II!) by treatment with the ylid prepared from a chloroether of the Formula (B )CHClOB (where B is lower alkyl and B is hydrogen or lower alkyl). The necessary chloroethers are obtained by standard treatment of aldehyde acetals of the formula (B )CH(OB with an acid chloride (J. Org. Chem. 1, 231. 1936).

Treatment of Compounds Ila in this fashion with the ylid from chloromethyl ether, for example, converts the keto group to a methoxymethylene group, which may be reduced to methoxymethyl. The latter group may be carried through the subsequent steps herein described to the 6-methoxymethyltetracycline. At this point, the elements of methanol may be split out by standard procedures to obtain the 6-methylene-6-deoxy-fi-demethyltetracycline.

The products of the above reaction may in turn be hydrogenated with noble metal catalysts:

l c02rt. UMCOQIM Subjecting the reduction products to the further synthetic sequences illustrated herein yields tetracyclines having a 6-OH(B )OB substituent. Treatment of such tetracyclines with liquid hydrogen fluoride results in the elimination of a mole of alcohol B OH and provides tetracyclines having a-CH(B at the 6-position. The latter treatment is, for example, conveniently effected after the introduction of the 12a-hydroxyl group. Alternatively treatment of such tetracyclines having a 6-OH(B )OB groupconverts this group to CH(B )OH with concurrent hydrolysis of any ether groups in the aromatic D-ring.

The products of the Wittig reaction Ilb may also be hydrolyzed to aldehydes and the resulting aldehyde group in turn converted by catalytic hydrogenation to a hydroxymethyl group. The latter may be carried through the subsequent reactions of synthetic sequence with its free hydroxyl group, or preferably, in the form a lower alkyl ether.

As has been previously pointed out, normal discretion must be employed in subjecting certain of the substituted intermediates to the herein described reaction steps. In the base condensation reactions, the presence of a substituent having an active hydrogen (e.g., a hydroxyl or amino group) will necessitate the use of an additional mole of the sodium hydride or other base. The presence of more than one such substituent per molecule is preferably avoided in these reactions, e.g. by the use of protective ether groups as previously described. The same considerations apply to Grignard reactions and hydride reductions. Hydroxyl groups can be subsequently regenerated from their ethers by conventional hydrolytic procedures such as treatment with hydrogen bromide. Similarly, protective benzyl ether groups can subsequently be lgydrogenolyzed to obtain hydroxyl groups where desire In addition, alternative routes or procedures can be selected. Thus, in the reduction of benzoyl adipate Ila to corresponding benzyl derivative 11, the three-step procedure previously referred to is an appropriate alternative to direct reduction; i.e. (1) conversion of the keto group to hydroxyl, e.g. with sodium borohydride or by mild reduction at room temperature with palladium on carbon in alcohol or other neutral solvent; (2) conversion of the resulting alcohol to the unsaturated compound by dehydration in anhydrous hydrogen fluoride; and (3) rapid hydrogenation of the resulting double bond, e.g. with palladium at room temperature and moderate hydrogen pressure, until one mole of hydrogen has been consumed. An alternative reduction procedure which is suitable is the Wolf-Kishner reaction (Annalen, 394, 90, 1912 and J. Russ. Phys. Chem. Soc. 43, 582, 1911) wherein the benzoyl derivative is converted to a hydrazone, and the latter is in turn reduced to the corresponding benzyl derivative by heating with a base such as sodium ethoxide.

Of particular value are compounds of the following formula:

XrA H l (5R 6 OH in which X, X R, and A are as described above, since these compounds are suitable for the preparation of known tetracycline compounds, i.e. where OR is OH, and homologs and analogs thereof.

These compounds are prepared from the corresponding starting compounds of structure II represented by structure IIc.

X1 A H X C 0 R:

A C OzRz (IIc) through the sequence represented by II III lV- I. In the ring closure reaction to corresponding structure III compounds, it is preferred that one of the benzenoid substituents (X or X be para to substituent OR so that the ring closure reaction proceed in the position ortho to substituent OR to afford corresponding structure III compounds. If there is no substituent para to OR a halogen group may be introduced by direct halogenation by conventional methods as hereinbefore described. The para halogen substituent may be removed, if desired, by hydrogenolysis, under the usual conditions, of the tetralone resulting from the ring closure.

The ring closure of compounds of structure IIa that have no substituent in the position para to OR, results principally in compounds of the following structure:

Structural Ila compounds are suitable for conversion to corresponding compounds of structure IV. They also provide an elegant method of introducing a variety of substituents into the position para to substituent OR as follows. The oxime of the tetralone (IIIa) is prepared by conventional methods and then subjected to the Beckman rearrangement (BF in HOAC) to the carboxamide:

which, on hydrolysis, provides structure IIa compounds with an amino group para to substituent OR. If desired, other substituents may be substituted for the amino group by diazotization and replacement of the diazonium group as previously described.

The present invention provides a means of synthesizing tetracycline compounds including new tetracyclines, not previously described, which are therapeutically useful by virtue of their antimicrobial activity.

Those skilled in the art will appreciate that the following examples provide a basis for preparing the listed tetracyclines and the corresponding 12a-deoxy derivatives thereof.

Some of the new tetracyclines of the present invention are homologs, isomers or closely related analogs of known tetracyclines. Many of the new tetracyclines are distinguished from prior art compounds by their possession of important and desirable properties, such as extended in vitro and in vivo antibacterial spectra, activity against organisms which have inherent or acquired resistance to known antibiotics, rapid absorption, sustained blood levels, freedom for serum binding, preferential tissue distribution at various parts of the body (e.g. kidney, lung, bladder, skin, etc.) which are sites for infection, sustained stability in a variety of dosage forms, resistance to metabolic destruction, broad solubility, and freedom from objectionable acute and cumulative side-effects. The new tetracyclines are useful in therapy, in agriculture, and in veterinary practice both therapeutically and as growth stimulants. In addition, they may be employed as disinfectants and bacterisostatic agents, in industrial fermentations to prevent contamination by sensitive organisms, and in tissue culture, e.g. for vaccine production.

The various new tetracyclines of the present invention which do not share the antibacterial activity of the known tetracyclines are valuable intermediates in the preparation of other compounds of classes known to contain biologically active members. Thus, the D-ring can be nitrated directly and the nitro derivative reduced catalytically to an aminotetracycline. Further, the tetracycline products of this invention can be halogenated by known methods at the 1la-, or in the case of a 7-unsubstituted tetracycline, in the 7,1la-positions by treatment with such halogenating agents as perchloryl fluoride, N-chlorsuccinimide, N-bromsuccinimide and iodobromide.

The present invention embraces all salts, including acidaddition and metal salts, of the new antibiotics. Such salts are formed by well known procedures with both pharmaceutically acceptable and pharmaceutically unacceptable acids and metals. By pharmaceutically aceptable is meant those salt-forming acids and metals which do not substantially increase the toxicity of the antibiotic.

The pharmaceutically acceptable acid addition salts are of particular value in therapy. These include salts of mineral acids such as hydrochloric, hydriodic, hydrobromic, phosphoric, metaphosphoric, nitric and sulfuric acids, as well as salts of organic acids such as tartaric, acetic, citric, malic, benzoic, glycollic, gluconic, gulonic, succinic, arylsulfonic, e.g. p-toluenesulfonic acids, and the like. The pharmaceutically unacceptable acid addition salts, while not useful for therapy, are valuable for isolation and purification of the new substances. Further, they are useful for preparation of pharmaceutically acceptable salts. Of this group, the more common salts include those formed with hydrofluoric and perchloric acids. Hydrofluoride salts are particularly useful for the preparation of the pharmaceutically acceptable salts, e.g. the hydrochlorides, by solution in hydrochloric acid and crystallization of the hydrochloride salt formed. The perchloric acid salts are useful for purification and crystallization of the new products.

Whereas all metal salts may be prepared and are useful for various purposes, the pharmaceutically acceptable metal salts are particularly valuable because of their utility in therapy. The pharmaceutically acceptable metals include more commonly sodium, potassium and alkaline earth metals of atomic number up to and including 20, i.e., magnesium and calcium and additionally, aluminum, zinc, iron and maganese, among others. Of course, the metal salts include complex salts, i.e. metal chelates, which are well recognized in the tetracycline art. The pharmaceutically unacceptable metal salts embrace most commonly salts of lithium and of alkaline earth metals of atomic number greater than 20, i.e., barium and strontium, which are useful for isolating and purifying, the compounds.

It will be obvious that, in addition to their value in therapy, the pharmaceutically acceptable acid and metal salts are also useful in isolation and purification.

The new tricyclic intermediates of the present invention, in addition to their value in synthesis, exhibit valuable antimicrobial activity. They may be employed as bacteriostatic agents, and are further useful in separation and classification of organisms for medical and diagnostic purposes. These new intermediates, by virtue of their fl-diketone structure, are also valuable chelating, complexing or sequestering agents, and form particularly stable and soluble complexes with polyvalent cations. They are therefore useful wherever removal of such polyvalent ions is desired, e.=g., in biological experimentation and in analytical procedures. Of course, as is well known to those skilled in the art, such fl-diketones may exist in one or more of several tautomeric forms as a result of their ability to enolize. It is fully intended that the B-diketone structures herein employed embrace such tautomers.

The starting compounds of the present invention are readily preparable by known procedures. Many of these compounds, including both benzoic acid esters and benzophenone starting compounds, have been described in the literature.

The following examples aregiven by way of illustration and are not to be construed as limitations of this invention, many variations of which are possible within the scope and spirit thereof.

EXAMPLE I Monoethyl ester of 3-(3-methoxybenzyl)adipic acid Method A.-Five grams of diethyl 3-(3-methoxybenzoyl)adipate and 2 g. of 5% palladium on carbon in 30 ml. of acetic acid are treated in a conventional Parr shaker at a pressure of 40 p.s.i. of hydrogen gas at 50 C. until 2 moles of hydrogen are taken up. The first mole of gas is taken. up rapidly and the second more slowly over a total reaction time of up to about 30 hours. The mixture is filtered, concentrated under reduced pressure to an oil which is vacuum-distilled to obtain the product.

Method B.The 'y-lactone of the enol form of the monoethyl ester of the starting compound is hydrogenated over palladium on carbon by this same method to obtain this product, B.P. l C. (0.3 mm.).

Elemental analysis gives the following results: Calcd. for C H O (percent). C, 65.29; H, 7.53. Found (percent): C, 65.25; H, 7.68.

The corresponding diethyl ester is prepared by refluxing this product in ethylene dichloride containing ethanol and sulfuric acid. The diester is obtained by diluting the reac:

23 tion mixture with water, separating, drying and concentrating the ethylene dichloride layer, and 'aeuum-distilling the residual oil n l.4973.

Elemental analysis gives the following results: Calcd. for C ll-1 (percent): C, 67.06; H, 8.13. Found percent): C, 67502; H, 8.31.

The starting compound together with the corresponding 'y-lactone are prepared by hydrolysis and decarboxylation of diethyl 3-carbo-t.butoxy-3-(3-methoxybenzoyl)adipate (Example L) by refluxing in dry xylene containing p-toluenesulfonic acid. The products are separated by fractional distillation or may be used together as starting compound forthis hydrogenation reaction.

EXAMPLE II 3- 3-methoxybenzyl adipic acid Method A.Amalgamated zinc is prepared by shaking for 5 minutes a mixture of 120 g. of mossy zinc, 12 g. of mercuric chloride, 200 ml. of water and 5 ml. of concentrated HCl in a round-bottomed flask. The solution is decanted and the following reagents added: 75 ml. of water and 175 ml. of cone. HCl, 100 ml. of toluene and 52 g. of 3-(3-methoxybenzoyl)adipic acid. The reaction mixture is vigorously boiled under reflux for 24 hours. Three 50 ml. portions of concerated HCl are added at intervals of 6 hours during reflux.

After cooling to room temperature, the layers are separated, the aqueous layer diluted with 200 ml. of water and extracted with ether. The ether extract is combined with the toluene layer, dried and concentrated under reduced pressure to obtain the product.

Method B.A solution of 5254.4 grams (22.1 mole) 3- (3-methoxybenzoyl)adipic acid in 38.5 liters of glacial acetic acid is hydrogenatedin a gal. stirred autoclave in the presence of 2.5 kg. 5 percent palladium-on-carbon catalyst at 1000 p.s.i.g. and 50 C. until the theoretical amount of hydrogen has been absorbed. The catalyst is filtered oh and the solvent removed from the filtrate by distillation at reduced pressure. This gives 5432 grams of product in the form of an oil. It is further purified by conversion to the dimethyl ester, fractional distillation, and hydrolysis, as follows:

methanol, 10.6 liters ethylenedichloride and 106 ml. con- 0 centra' ted sulfuric acid isstirred and refluxed for 15 hours.

The mixture is cooled and washed with water (3X5 1.), 5 percent aqueous sodium hydroxide (1 x2 1.) and again with water (3X5 1.). The ethylenedichloride solution is dried over 3 lb. anhydrous magnesium sulfate (with 2 lb. Darco G60 activated carbon). The dry ng agent. and carbon are filtered off and the filtrate concentrated at reduced pressure to remove solvent. The residue is distilled through a 3 x 16" vacuum-jacketed fractionating column packed with porcelain saddles. After a forerun of 934.1 grams, the t drolysis mixture is acidified to pH ca. 1.0 by addition of concentrated hydrochloric acid and the product is extracted into methylene chloride (1X4 1. and 2X2 1.). The methylene chloride extract is washed with Water (1X4 l.+1 8 1.), dried over magnesium sulfate, filtered and free of solvent by distillation at reduced pressure; This gives 2506 grams of 3%3-methexybenzyl)adipic acid in the form of a very sticky oil. 7 Method C.A solution of dimethyl 3-(3-methoxybenzyl)adipate (0.01 mole) in 280 ml. of 1:1 tetrahydrofuran:1,2-dimethoxyethane at a temperature of about 10 C. is treated with a solution of sodium borohydride (0.005 mole'i in ml. of 1,2-dimethoxyethane and 10 ml. of water. After 15 minutes, 5.ml. of glacial acetic acid is added and the mixture stirred for 5 minutes. Hydrochloric acid (3 ml. of 6 N) is then added, the mixture stirred for an additional 0.5 hour,"then poured into water. The product, 3-[a-hydroxy-(3-methoxybenzyl)]adipic acid dimethyl ester, is recovered by evaporation. 5 The hydroxy ester is placed in 150 ml. of anhydrous hydrogen fluoride and allowed to stand overnight. The hydrogen fluoride is then evaporated and the thus produeed dimethyl 3-(3-methoxy benzylidene)adipate dissolved in dioxane (300 ml.)=, treated with 0.3 g. of palladium on charcoal (5%) and subjected to p.s.i. at room temperature until an equimolar proportion of hydrogen is consumed. The mixture is filtered and the filtrate evaporated to dryness under reduced pressure to give the desired compound as the methyl ester. It is hydrolyzed to 15 the acid by the procedure of Method B.

EXAMPLE HI Dirnethyl 3- 2-chloro-5-methoxybenzyl adip ate Method A.A mixture of 3.2 g. of dimethyl 3-(3- methoXybenzyDadipate and 1.4 g. of N-chlorosuccinimide in 30 ml. of trifluoracetic acid is stirred and heated on a steam bath for 30 minutes. The reaction mixture is then poured into 5% aqueous sodium bicarbonate with stirring, and the mixture extracted with ether. The combined extracts are dried over anhydrous sodium sulfate and then concentrated under reduced pressure to an oil which is vacuum-distilled to obtain the product, B.P. 200 C. (1.1 mm. Hg).

Method B.A mixture of 3.2 g. of dimethyl 3-(3- methoxybenzyl)adipate and 2.1 g. of phosphorus pentachloride in 100 ml, of dry benzene, is refluxed for 30 minutes. The reaction mixture is carefully poured into ice and water, the benzene layer separated, washed with water and dried, Concentration of the dried benzene solution under reduced pressure yields an oil which is vacuumdistilled to obtain the product. I

Similarly, the diethyl, dibenzyl and dipropyl esters are .prepared. H 1

Method C.--A solution of 1688 g. of '3-(3-methoxybenzyliadipic acid and 50 mg. of iodine in 9 liters of glacial acetic acid is stirred whileja solution of 450 g. of chlorine in 8 liters of glacial acetic acid is added during about 2 hours; The mixture is kept in the dark during the procedure and the temperature maintained at 1015 C. The solvent is then removed by concentration under reduced pressure to give 1902 of a dark amber oil.

This procedure is repeated with ferric chloride in lieu of iodine with comparable results.

Method B.A mixture of 30.4 g. of diethyl 3-(3- methoxybeniyDadipate and 12.75 g. of sulfuryl chloride in 250 ml. of benzene is allowed to stand for 3 days at room temperature. At the end of this period, the reaction mixture is concentrated under reduced pressure to a gummy residue which is vacuum-distilled to obtain the product.

Method E.The procedure of Method B is repeated using as starting coinpound the corresponding dicarboxylic acid to obtain 3-(2-chl0ro-S-methoxybenzyl)adipic acid dichloride. g 1

EXAMPLE E Diethyl 3- (2-chloro-5-ethoxybenzyl)adipate Thisiproduct ,is'obtained by the procedure of Method A of Example III employing diethyl 3-(3 -ethoxybenzyl) O adipate in lieu of dimethyl 3-(3-methoxybenzyl)adipate.

EXAMPLE V 2-(f-earbetlioxyethyl)-5-methoxy-8-chh)ro-4-tetralone Method A.A mixture of 2 g. of diethyl-3-(2=chloro-5- methoxybenzyhadipate (Example III) .and 30 g;;of polyphosphoric acid is heated on a steam bath for 30 minutes and then poured into ice Water. The oil then separates and is collected. a.

Method B.-A mixture of 2.0 g. of the di-acid chloride 75 ofi3-(2-chloro-5-methoxybenzyl)adipic acid in 30 ml. of

carbon disulfide is cooled to C. and 4 g. of aluminum chloride added portionwise to the cooled mixture. The mixture is stirred for 30 minutes and then allowed to warm to room temperature where a vigorous reaction ensures. After the vigorous reaction subsides the mixture is warmed on a steam bath, cooled, diluted with water and the carbon disulfide steam distilled. The mixture is extracted with chloroform and the product obtained by drying and concentrating the chloroform extract. The product is the free acid which, if desired, is converted to the desired lower alkyl ester by conventional methods. For example, the methyl ester is prepared as follows:

A mixture of 2002 g. (7.1 moles) of the tetralone acid, 3 l. chloroform, 682 g. (21.3 mole) methanol and 21.2 ml. conc. sulfuric acid is refluxed with stirring on a steam bath for 20 hours. The reaction mixture is then chilled and 2 1. each of chloroform and water are added. The organic phase is separated and washed successively with 2x 21. water, 1X 1 l. 21% aqueous sodium hydroxide and 3 X 4 1. water to a final pH of about 7.5. After drying over anhydrous sodium sulfate and treatment with Darco KB activated carbon the solution is iiltered and concentrated to a dark oil at reduced pressure. The oil is taken up in 6 1. hot ethyl acetate and 11 l. hexane added. The solution is chilled to C. with stirring and 1404 g. 2-(2- carbomethoxyethyl)5-methoxy-8-chloro 4 tetralone recovered by filtration, hexane-washing and air-drying. The product melts at 101.0-'2.4 C.

EXAMPLE VI 2- (Z-carboxyethyl) 5-methoxy-8chloro-4-tetralone A polyethylene container is charged with 1809- g. (6.03 mole) 3-(2-chloro-5methoxybenzyl) adipic acid and chilled in an ice bath while 7 kg. liquid hydrogen fluoride is introduced from an inverted, chilled tank. The mixture is swirled to make homogeneous and then left to evaporate partially overnight in a hood. Most of the hydrogen fluoride that remains is removed by placing the polyethylene container in warm water to cause rapid evaporation. The remainder is removed by quenching in about 10 1. water. The product is then extracted into chloroform, washed with water and dried over magnesium sulfate. Removal of the drying agent by filtration and the solvent by distillation gives a gum that is triturated with ether and filtered. This gives 1031 g. of crude product that is recrystallized from a mixture of 161. ethanol, 2 l. acetone and 1 l. ethylene dichloride, with activated carbon treatment. The first two crops amount to 86 3.9 grams of white crystalline product melting at l-'75.0180.5 C.

Elemental analysis gives the following results: Calcd. for C H O Cl (percent): C, 59.47; H, 5.35; Cl, 12.54. Found (percent): C, 59.51; H, 5.42; Cl, 12.60.

Ultraviolet absorption shows A max at 223 111 1. (e=24,650), 255 m (15:7,900) and 32611'1 1. (e=4,510=). Infrared absorption maxima appear at 5.76 and 5.99 [.L.

This product is also obtained by hydrolysis of the product of Method A, Example V, by treatment with HCl in acetic acid.

The methyl ester, ethyl ester (m. 57-59 C.) and benzyl ester (m. 84-85" C.) are prepared by conventional methods.

3-(3-methoxybenzyl)adipic acid, treated with HF as described, yields 2-(2-carboxyethyl)7-methoxy-4-tetralone, which melts at 158-9 C. after two recrystallizations from benzene-hexane and exhibits ultraviolet absorption maxima at 225 mg (e=l3,500) and 276 m 16,000) in methanolic HCl and NaOH.

Analysis.-Calcd. for C H O (percent): C, 67.73; H, 6.50. Found (percent): C, 67.67; H, 6.48.

EXAMPLE VII 2- Z-carboxyethyl -6-chloro-7 methoxy-4-tetralone This substance is a byproduct of the cyclization of the products of Example 111. It is separated from. the crude 2-(2-carboxyethyl)5-methoxy-8chloro-4-tetralone of Ex ample VI by virtue of its chloroform insolubility. 2900 g. of the crude tetralone are leached six times with 8 liter portions of hot chloroform. 170 g. of white solid remain, melting at 236239 C. The methyl ester is prepared by the procedure of Example V, Method B.

EXAMPLE VIII 2-(2-carbomethoxyethyl)5-benzyloxy-8-chloro- 4-tetralone 2- (2-carboxyethyl) 5-methoxy-8chloro-4-tetralone (25 g.), glacial acetic acid (200 ml.) and 48% hydrobromic acid (50 ml.) are heated at under nitrogen for twenty-four hours. The cooled solution deposits a crystalline solid. The mixture is poured over two parts ice and the total solid crop isolated by filtration and thoroughly washed with water. The crude 2-(2-carboxyethyl)-5-hydroxy-8chloro-4-tetralone obtained in this way is recrystallized from acetonitrile to obtain 18.8 g. melting at 164-8 C.

Elemental analysis: Calcd. for C H CIO (percent): C, 58.11; H, 4.88; Cl, 13.20. Found (percent): C, 57.99; H, 4.87; Cl, 12.73.

14.5 g. of this product is placed in 200' ml. dry methanol and the mixture refluxed for 30 minutes as anhydrous HCl is passed through. The now clear yellow solution is allowed to stand overnight, and the methanol is then removed in vacuo. The residual gum is extracted exhaustively with hexane and the combined extracts are concentrated and cooled. 11.8 g. of the white, crystalline methyl ester separates and is filtered off and recrystallized from hexane.

The ester melts at 6869.5 C. and analyzes as follows: Calcd. for C H CIO (percent): C, 59.45; H, 5.35; Cl, 12.6 Found (percent): C, 59.16; H, 5.38; Cl, 12.6.

5.6 g. (0.02 mole) of this substance is dissolved in 500 ml. anhydrous methanol and to this is added 0.02 mole sodium methoxide and 500 ml. benzene. The mixture is concentrated to dryness in vacuo at room temperature, then heated at C. and 0.1 mm. for 10 minutes. The residue is maintained under high 'vacuum at room temperature for 16 hours, and the dry solid added to 50 ml. benzyl bromide together with sufiicient dimethyl formamide to solubilize. The mixture is heated at 100 C. for 48 hours with stirring, then cooled and filtered. The filtrate is concentrated at reduced pressure and the residual oil chromatographed on acetone-washed and dried silicic acid in chloroform. The first efiluent fraction consists of unchanged starting material. The main fraction recognized by a negative ferric chloride test, deposits crystalline Z-(Z-carbomethoxy ethyl) 5 benzyloxy-8r-chloro4-tetralone on standing.

EXAMPLE IX 2carbomethoxy-S-methoxy-8-chloro-3,4, 10-trioxo- 1,2,3,4,4a,9,9a,10-octahydroanthracene 30 grams of 2-(2-carbomethoxyethyl)5-methoxy-8- chloro-4-tetralone (0.1 mole), prepared as described in Example V, Method B, is dissolved together with 24 grams dimethyloxalate (0.2 mole) by warming with 135 ml. freshly distilled dimethyl formamide in a well dried two liter flask which has been flushed with dry nitrogen. The solution is cooled to 20 C. and to it is added all at one time 0.4 mole sodium hydride in the form of a 50% oil dispersion which has been exposed to the atmosphere for 24 hours in order to produce a deactivating coating. The reaction mixture is maintained at 20 25 C. with an ice bath. 0.1 mole dry methanol is now added, and the temperature rises spontaneously to 40-50 C. When the temperature begins to fall (about 5 minutes after addition of the methanol) the reaction vessel is removed from the ice bath and quickly placed in an oil bath at C. The reaction temperature is brought with dispatch to 90 C. and maintained there for a maximum of 10 minutes or until active bubbling ceases.

The flask is now immediately transferred back to the ice bath, and when the temperature reaches C., 100 ml. of glacial acetic acid is added at such a rate that the temperature does not exceed 30 C. At this point, a golden yellow precipitate appears. 150 ml. methanol and 50 ml. water are added and the mixture is digested at 45 C. for 15 minutes and then stirred in an ice bath for an hour. If only a scanty crop of crystals is present at this time the mixture may be stored in the refrigerator overnight before proceeding. It is now transferred to a separatory funnel to permit separation of the oil from the sodium hydride oil dispersion. The suspension is then filtered with suction, and the filter cake triturated three times with 100 ml. portions of hot hexane to extract impurities. The washed solid is next stirred with 200 ml. water, filtered, and then digested with 500 ml. refluxing methanol for minutes, to effect further purification. 1Sl6 grams of bright yellow needles are obtained. The product melts at 200-205 C. and exhibits no carbonyl absorption below 6 In 0.01 N methanolic HCl it exhibits ultraviolet absorption maxima at 406 my. (e=14,200) and at 275-290 mg (e -5,940). In 0.01 N methanolic NaOH it exhibits maxima at 423 mu (e=13,950) and at 340 m (e=7,120).

EXAMPLE X 2-carbomethoxy-6-chloro-7-methoxy-3,4,10-trioxo- 1,2,3 ,4,4a,9,9a,10-octahydroanthracene 2-(2-carbomethoxyethyl) -6-chloro-7-methoxy 4 tetralone prepared in Example VII, 30 g., is dissolved in 24 g. dimethyl oxalate in 300 ml. dry distilled dimethyl formamide by warming. The solution is then cooled under nitrogen in an ice-salt bath and 19.86 g. sodium hydride (51.2% in oil) added all at once as the temperature is maintained below 20 C. The ice bath is removed and the temperature rises spontaneously to 30 C., whereupon the bath is replaced briefly to control the vigorous reaction. The reaction mixture is then heated to 7080 C. for 5-8 minutes, cooled to below 0 C., and treated with 100 ml. acetic acid, added at such rate that the temperature does not reach C. The reaction mixture is now poured into four volumes of chloroform. The chloroform solution is washed with water, then with saturated brine, and dried over anhydrous sodium sulfate. The solvent is removed in vacuo, and the residue is treated with 350 ml. methanol. After standing for several hours at room temperature the slurry is filtered to obtain 12.5 g. yellow crystalline product, melting at 228-231 C. with decomposition and gas evolution. Recrystallization from chloroform-methanol raises the melting point to 2356-2368 C.

Analysis.Calcd. for C H O CI (percent): C, 58.21; H, 4.31; CI, 10.11. Found (percent): C, 58.53; H, 4.43; Cl, 10.10.

EXAMPLE XI 2-carbobenzyloxy-5-methoxy-8-chloro-3 ,4, IO-trioxo- 1,2,3,4,4a,9,9a,10-octahydroanthracene 2-(2-carboxyethyl)-5-methoxy-8-chloro 4 tetralone, 0.02 mole, is combined with 500 ml. anhydrous methanol and to this is added 0.02 mole sodium methoxide and 500 ml. benzene. The mixture is concentrated to dryness in vacuo at room temperature, then heated at 100 C. and 0.1 mm. for 10 minutes. The residue is maintained under high vacuum at room temperature for 16 hours, and the dry solid added to 50 ml. benzyl bromide together with sufiicient dimethyl formamide to solubilize. The mixture is heated at 100 C. for 48 hours with stirring, then cooled and filtered. The filtrate is concentrated under reduced pressure to obtain the benzyl ester as residue. Purification is efiected by washing of a chloroform solution with aqueous sodium bicarbonate.

This substance is dissolved together with 0.04 mole dibenzyl oxalate in 50 ml. dry, distilled dimethyl formamide. To this is added 0.08 mole sodium hydride in the form of a 50% oil dispersion, while maintaining the temperature at about 20-25 C. Benzyl alcohol, 0.02 mole, is added, and the mixture is heated to C. for 5 minutes, then cooled to 20 C. and slowly acidified with glacial acetic acid. The reaction mixture is next evaporated to dryness under reduced pressure and the residue is taken up in chloroform. The chloroform solution is washed with water, then with brine, dried over sodium sulfate, treated with activated carbon and filtered. The filtrate is evaporated at reduced pressure to obtain the product as residue. It is purified by evaporation of the highly fluorescent, less polar eluate fraction from silicic acid chromatography in chloroform.

EXAMPLE XII Z-carbomethoxy-S-methoxy-8-chloro-3 ,4,10-trioxo- 1,2,3,4,4a,9,9a,10-octahydroanthracene Clean sodium metal (3.68 g.) is dissolved in methanol (50 ml.) and the solution evaporated to a dry white solid in vacuo (this is most successfully carried out by using rotary vacuum equipment). Dimethyloxalate (9.44 g.) and benzene ml.) are then added to the flask and refluxing is carried out for about 10 minutes under nitrogen (not all of the solids dissolve but the cake is broken up). The solution is cooled and dimethylformamide (50 ml.) then added followed by the dropwise addition of a solution of 2-(2-carboxyethyl)-5-methoxy 8 chloro 4- tetralone (Example VI) (11.3 g.) in dimethylformamide (100 ml.) during one hour at 20 under N with stirring, and stirring at room temperature under N is continued overnight. The solution is then poured into cold water (1 l.) and extracted twice with chloroform. The chloroform extract is discarded and the aqueous solution acidified with 10% HCl solution. The product is obtained by extraction with chloroform (3X 200 ml.), back-washing once with water, drying Over anhydrous Na SO treatment with charcoal, filtration and evaporation of the solvent in vacuo to give a red gum (16.4 g.) which is 2-(2-carboxyethyl) -3-methyloxalyl-5-methoxy 9 chloro- 4-tetralone.

U.S. absorption maxima in 0.01 N NaOH at 258 and 363 III/1.. Maximum in 0.01 N HCl at 347 mg, minimum at 277 mg.

The gum gives a deep red color with ferric chloride in methanol and liberates CO from a saturated NaHCO solution.

The acid is esterified by dissolving in chloroform (1 1.), methanol (50 ml.) and conc. H SO (10 ml.) and refluxing gently for 15 hours. The solution is cooled, poured into excess water and the chloroform layer separated. The aqueous layer is extracted with chloroform (250 ml.) and the combined chloroform extracts are backwashed twice with cold water. The extract is then dried over anhydrous sodium sulphate, treated with activated charcoal, filtered and evaporated to a red gum in vacuo. This gum does not liberate CO from saturated bicarbonate solution, and gives a deep red color with ferric chloride in methanol.

The ester product, 3.825 grams, and 1.275 g. of sodium hydride (56.5% solution in oil) are dissolved in 25 ml. of dimethylformamide. An exothermic reaction sets in with the evolution of hydrogen gas. After the evolution of gas ceases the mixture is warmed at 40 C. for /2 hour where further evolution of hydrogen gas occurs and the reaction mixture darkens. The reaction mixture is finally digested on a steam bath for 10 minutes after which it is cooled and acidified with glacial acetic acid (15 ml.). The product is then obtained by dilution of the mixture with water followed by extraction with chloroform. The dried chloroform solution is concentrated under reduced pressure to obtain a gummy residue which crystallizes on trituration in methanol. The orange-yellow crystalline product, 2-carbomethoxy-5-methoxy 8 chloro 3,4,10- trioxo 1,2,3,4,4a,9,9a,10 octahydroanthracene, 1.2 g.) melts at l96201.5 C.

29 EXAMPLE xrn 2-carbomethoxy-5-hydroxy-8-chloro-3,4,10-trioxo- 1,2,3,4,4a,9,9a,10-octahydroanthracene Dimethyl oxalate, 0.84 g., and 2-(2 canbomethoxyethyl)-5-hydroxy-8-chloro-4-tetralone, 2.0 g. ,are added to a suspension of 0.34 g. sodium hydride in 10 ml. dimethyl formamide and the mixture is heated to 70 C. for three minutes. After cooling, the reaction mixture is treated with 10 ml. acetic acid and evaporated to dryness at reduced pressure. The residual gum is triturated with Water to remove sodium acetate and chromatographed on silicic acid in chloroform. The main effluent fraction is dried to a bright yellow solid which is crystallized from chloroformhexane to provide 380 mg. product melting at 218- 219.5 C.

Elemental analysis, calculated for C H O Cl (percent): C, 56.7; H, 3.9; CI, 10.5. Found (percent): C, 56.86; H, 3.89;Cl, 10.8.

EXAMPLE XIV Diethyl .3- a-hydroxy-3-methoxybenzyl) adipate This product is obtained by treating 5 g. diethyl 3-(3- methoxybenzoyl) adipate and 2 g. 5% palladium on carbon in ethanol with 40 p.s.i. hydrogen gas at room temperature until one molar equivalent of hydrogen is consumed. The reaction mixture is filtered and concentrated at reduced pressure to obtain the product.

It is further converted to diethyl 3-(a-N,N-dimethylamino-3-methoxybenzyl)adipate in the following manner:

The a-hydroxy benzyl adipate ester, 0.01 mole in 15 ml. dimethoxyethane, is added to a stirred mixture of 1.9 g. (0.01 mole) p-toluenesulfonyl chloride and 2.5 ml. dry pyridine in an ice bath. When the reaction subsides the mixture is permitted to warm to room temperature, stirred for three hours, and poured into 50 ml. water. The pH is adjusted to 5 and the resulting tosyl ester recovered by filtration.

The tosylate (0.0025 mole) is combined with 25 ml. dimethoxyethane and added dropwise to a stirred solution of 0.015 mole dimethylamine in 50 ml. dimethoxyethane at C. After addition is complete, stirring is continued for an hour at 0 and the reaction mixture is then heated at 60 for three hours under a Dry Ice condenser;

The mixture is next evaporated in vacuo and the residue washed with water to remove dimethylammonium toluenesulfonate. The product is recovered by filtration from the water. Substitution of monomethylamine for dimethylamine in this procedure provides the corresponding a-N- methylamino derivative.

EXAMPLE XV 2-(2-carbomethoxyethyl)-5-methoxy-4-tetralone 2 (2 carbomethoxyethyl) -methoxy-8-chloro-4- tetralone (1.5 g.) is combined with 5% palladium-oncharcoal (0.37 g.), triethylamine (0.5 g.) and methanol 270 ml. in a standard Parr hydrogenation bottle and subjected to fifty pounds of hydrogen pressure. The absorption of hydrogen levels oil. at approximately one molar equivalent. The catalyst is filtered off, the solution taken to dryness, and triethylamine hydrochloride is removed by washing with water. The residual white solids weigh 1.1 g. and melt at 63-66 C. After two recrystallizations from hexane and one from ether the product melts at 85-87.

Analysis.Calcd. for C H O (percent): C, 68.68;- H, 6.92. Found (percent): C, 68.59; H, 6.98.

EXAMPLE XVI 2-(Z-carboxyethyl)-7hydroxy-4-tetralone 3-(-methoxybenzyl)adipic acid, 22.46 g., is heated at reflux with hydriodic acid (specific gravity 1.5) for 3 hours and the methyl iodide formed is separated. The

solution is evaporated in vacuo and the resulting gum triturated with cold water to yield 14.7 g. of yellow crystalline product. Dried and recrystallized from aqueous acetone the product is obtained in the form of white crystals melting at 183.5185.5 C.

Analysis.-Calcd. for C H O (percent): C, 66.65; H, 6.02. Found (percent): C, 66.60; H, 6.02.

The same product is obtained by refluxing a mixture of 0.5 g. of the 3-(3-methoxybenzyl)adipic acid with 25 ml. 48% for 18 hours, then pouring the reaction mixture into 3 volumes of water, and filtering the resulting 0.4 g. of crystalline precipitate.

EXAMPLE XVII 2-(Z-carbomethoxyethyl)-5-methoxy-8-nitro-4-tetralone One gram of the Example XV product is slowly added to 10 ml. of concentrated sulfuric acid containing 2 ml. of 70% nitric acid at a temperature of 05 C. The solution is stirred for 15 minutes and allowed to warm to room temperature. The mixture is poured into ice-water mixture and extracted with chloroform, the chloroform layer separated, dried and concentrated to obtain the product.

EXAMPLE XVIII 2-(2-carboxyethyl-5-hydroxy-8-amino-4-tetralone One molecular proportion of aniline is dissolved in 2 N HCl, employing about 20 ml. thereof per gram of aniline, and the solution treated with one molecular proportion of NaNO at 0 to 10 C. The benzenediazonium chloride solution is then mixed with stirring at 0 to 20 C. with an aqueous solution of 2-(2-carboxyethyl)- 5-hydroxy-4-tetralone sodium salt and suflicient sodium carbonate to neutralize the excess HCl in the diazotised aniline solution. The pH of the solution is in the range 8-10. Stirring is continued at 0 C. for approximately two hours after which careful neutralization of the reaction mixture yields the S-phenylazo compound. The product is collected on a filter, Washed and dried.

One part by weight of 2 (2-carboxyethyl)-5-hydroxy- 8-phenylazo-4-tetralone is mixed with 20 parts by Weight of methanol and /s part by weight of 5% palladium-oncarbon catalyst is added to the mixture which is then hydrogenated at 30-45 p.s.i. of hydrogen gas in a conventional shaker apparatus at 30 C. until two molar equivalents of hydrogen are taken up.

After filtration, the product is recovered by high vacuum distillation of the residue obtained by removal of the solvent in vacuo. Care must be exercised to protect the amino phenol from air. It can be stabilized by acetylation, as follows:

The crude amine is placed in 20 parts water containing one molar equivalent of HCl, and 2.2 molar equivalents of acetic anhydride are added. Sufficient sodium acetate is then added to neutralize the HCl and the solution is warmed to 50 C. After 5 minutes the mixture is cooled and the crude acetate separated by filtration. The solid is then dissolved in cold 5% sodium carbonate solution and reprecipitated with 5% HCl. The 2-(2-carboxyethyl)-5-hydroxy-8-N-acetylamino 4 tetralone obtained in this manner is a preferred form of the amino compound for further reaction sequences.

EXAMPLE XIX 3-(2-amino5-hydroxybenzyl) adipic acid The procedure of Example XVIII is repeated using 3- (3-hydroxybenzyl) adipic acid as starting compound t0 obtain this product. It may be converted to the product of Example XVIII by the ring closure procedure of Example VI.

EXAMPLE XX 3-(2-chloro-5-hydroxybenzyl) adipic acid Three parts by weight of the product of Example XIX (obtained by evaporating the methanol,- is protected from air, immediately mixed with parts by weight of 10% aqueous hydrochloric acid at 0 C., and diazotized by gradual addition of aqueous sodium nitrile solution. Addition of sodium nitrite is continued until a positive starch iodide test on a few drops of the reaction mixture is obtained in the convention fashion. The resulting solution is then added to 15 parts of a boiling 10% solution of cuprous chloride in aqueous hydrochloric acid. The mixture is boiled for 10 minutes and allowed to cool. The product separates from the cooled mixture and is collected in the conventional manner.

This procedure is used for the preparation of 3-(2- substituted 5 hydroxy benzyl) adipic acid compounds such as 2-bromo (using Cu Br and HBr), 2-iodo (using KI and H SO and 2-fiuoro compounds (decomposing the dry diazonium fiuoborate salt by careful heating).

E AMPL XXI a-hydroxy-u- (2-chloro-S-methoxy-phenyl ethyl] adipic acid diethyl ester 3- oc- 2-chloro-5 -methoxyphenyl ethyl] adipic acid diethyl ester The product of Example XXI, 2 g., is dissolved in 150 ml. of glacial acetic acid and hydrogenated at a pressure of 40 p.s.i. of hydrogen gas for 24 hours at room temperature in the presence or 2 g. of 5% palladium-in-carbon catalyst. The inixture is filtered and then concentrated. The product is obtained by vacuum distillation of the residue.

EXAMPLE XXIII l3,3 ',4-trimethoxybenzophenone A mixture of 40 g, of 3-methoxybenzoyl chloride, 32 g. of veratrole and 260 ml. of carbon disulfide in a 3 neck round bottom flask fitted with reflux and stirrer is cooled to 0 C. Then 40 g. of aluminum chloride is added portionwise to the cooled mixture and the mixture stirred for 45 minutes, after whichiit is allowed to warm to room temperature. A vigorous reaction ensues with the separation of a yellow precipitate. The, mixture is carefully warmedon a steam bath and stirred for 1 /2 hours. Water is then added to the cooled mixture and the carbon disulfide is steam distilled off. The resultant mixture is then extracted with chloroform and the chloroform layer separated, washed with dilute hydrochloriciacid, followed by dilute sodiu'rn hydroxide and then dried and concentrated under reduced pressure. The residual oil'is distilled to obtain'the product, B.Pf 216-218 C. at 1.5 mm.

mercury. A 65% yield of product is obtained. The viscous product is stirred in absolute methanol'and crystallizes, In. 85-86" C; f

' EXAMPLE XXIV 3;3',4-trimethoxydiphenylmethane Method A.A solution of 5 g. of 3,3',4-trimethoxybenzophenone in 200 ml. of ethanol containing 1 g. of copper chromium oxide is hydrogenated at 180 C. and 100 atmospheres of. hydrogen gas for 1.5 hours. Theresultant solution is filtered and concentrated under reduced pressure. The residual oil is distilled to obtain the product B.P. 192-194 C. at 2.5 mm. mercury. The product crystallizes on standing? the melting point of the crystals being 4546 C. Elemental analysis gives the following results: Calcd. for C d-E 0 (percent): C, 74.39; H, 7.02. Found (percent): C, 74.50; H, 7.18.

Method'B-This' product is also obtained by hydrogenation of the starting compound of Method A using 10% palladium on carbon in ethanol at 50 C. and 40 psi. of hydrogen gas. The hydrogenation procedure is also carried out at room temperature, although the uptake of hydrogen is considerably siower than at 50 0. The prodduct is obtained by filtration and concentration of the hydrogenation mixture. W

- I EX MPLE XXV 3,3 ,4-trihydroxydiphenylmethane Two grams of 3,3#l-trimethoxydiphenylmethane are dissoived in 10 ml. of acetic acid and 10 ml. of 48% hydrobromic acid and the mixture refluxed for 5 hours. The reactionmixture is concentrated under reduced pressure to obtain a residual gum which is vacuum-distilled (B.P. 230 C. at 0.5mm. of mercury). The distillate, a colorless gum, crystallizes. A 62% yield of product is obtained, In. l035-104 C. a 1;

EXAMPLE XXVI tracted with ethyl acetate. concentration of the ethanol acetate extract after drying gives the product as a gummy residue.

.in aqueous sodium hydroxide (4 molar equivalents)' and agitated with 3 molar equivalentsof dimethyl sulfate at 40 C. for 6 hours. The resultant solution is then diluted with water and extracted with chloroform. The chloroform layer is separated; dried and concentrated under reduced pressure to yield an oil, Bl. 205 to 210"; C. at 0.2 mm. mercury. This product is also obtained by treatment of the starting compound with diazomethane in diethyl ether. g

In a similar manner the corresponding ethyl and propyl esters are prepared.

H E AMPLE XXIX 3- 3-niethoxybenzyl hexa-2,4-dienedioic acid lFive grams of 3,3',4-trimethoxydiphenylmethane are dissolved in 50 ml. of acetic acid containing about 10 drops of water and ozonized air containing about 4% O is then passed into' the mixture for 1.5 hours (total .pf about 6 moles of ozone). The resultant yellow solution is pouredinto 1 liter of Water and extracted with chloroform. The chloroform layer is separated, washed with aqueous sodium bicarbonate solution and concentrated under reduced pressure. The residue is dissolved in ethanol containing 2 g. of KOH and the mixture allowed 33 to stand at room temperature for 2 days after which it is diluted with water and extracted with chloroform. After separation of the chloroform layer the aqueous alkaline solution is acidified with dilute hydrochloric acid and extracted with chloroform. Concentration of the chloroform extract gives the acid product.

The methyl, ethyl and propyl diesters of this acid are prepared by refluxing the acid for 3 days in ethylene dichloride containing the appropriate alcohol and sulfuric acid.

EXAMPLE XXX 3-(3-methoxybenzyl)adipic acid dimethyl ester EXAMPLE XXXI The following monoester compounds are prepared by reduction of corresponding benzoyl diesters according. to the methods of Example I. The free adipic acid derivatives are prepared by the methods of Example II from the corresponding benzoyl adipic acids. The products are subsequently converted to the corresponding diesters by conventional procedures, e.g. Example II, Method B.

3-benzyladipic acid monoethyl ester 3-(2-ethyl-5-hydroxybenzyl)adipic acid monoethyl ester 3-(2-chloro-5-methoxybenzyl)adipic acid monomethyl ester 3-(2-dimethylamino-5-methoxybenzyl)adipic acid monomethyl ester 3-(2-amino-5-methoxybenzyl)adipic acid 3-(Z-acetamido-S-methoxybenzyl)adipic acid 3-(3-hydroxy-benzyl)adipic acid monoethyl ester 3-(S-methyl-S-hydroxybenzyl)adipic acid monoethyl ester 3- 2,3-dimethyl-S-hydroxybenzyl) adipic acid monoethyl ester 3-(2-methyl-5-hydroxybenzyl)adipic acid monoethyl ester 3-(3-dimethylamino-S-hydroxybenzyl)adipic acid monoethyl ester 3-(2,3-dimethylbenzyl)adipic acid monomethyl ester 3-(3,5-dimethoxybenzyl)adipic acid monoethyl ester 3-(3-hydroxybenzyl)adipic acid monoethyl ester 3-(3-isopropyl-5-hydroxybenzyl)adipic acid monoethyl ester 3-(2,3-diethyl-5-hydroxybenzyl)adipic acid monoethyl ester 3-(5-benzyloxybenzyl) adipic monoethyl ester 3-(2-chloro-5-benzyloxybenzyl) adipic acid monoethyl ester 3-(3-propionyloxybenzyl)adipic acid monoethyl ester 3-(3-acetyloxybenzyl)adipic acid monoethyl ester 3-(2-amino-5-benzyloxybenzyl)adipic acid monobcnzyl ester 3-(2-propyl-5-propoxybenzyl)adipic acid monomethyl ester 3-(S-methoxy-Z,3-ditrifluoromethylbenzyl) adipic acid monomethyl ester 3-(2-trifluoromethyl-3,S-dibutoxybenzyl) adipic acid monoethyl ester 3-(Z-trifluoromethyl-S-ethylamino-5-methoxybenzyl) adipic acid monoethyl ester 3-(3-butyrylamidobenzyl)adipic acid monoethyl ester 3-(2-trifluoromethyl-S-hydroxybenzyl)adipic acid monobenzyl ester 3-(2-chloro-5-hydroxybenzyl)adipic acid monobenzyl ester 3-(2-chloro-3-methyl-5-hydroxybenzyl)adipic acid monoethyl ester 3-(2-chloro-3-isopropyl-S-hydroxybenzyl)adipic acid monoethyl ester 3-(2-chloro-3-amino-5-methoxybenzyl) adipic acid monoethyl ester 3-(2-chloro-3-methyl-5-methoxybenzyl)adipic acid monobenzyl ester 3-(2-chl0ro-3-ethyl-5-methoxybenzyl)adipic acid monobenzyl ester 3-(2-chloro-3-dimethylamino-5-hydroxybenzyl) adipic acid 3-(3,5-di-ethoxybenzyl)adipic acid monoethyl ester 3-(2-methylamino-5-propoxybenzyl)adipic acid monoethyl ester 3-(Z-methyl-S-hydroxybenzyl)adipic acid 3-(2-amino-5-benzyloxybenzyl)adipic acid monomethyl ester 3-(3-acetamido-5-hydroxybenzyl)adipic acid monoethyl ester 3-(2-chloro-3,5-dihydroxybenzyl)adipic acid monoethyl ester 3-(3-trifiuoromethyl-S-hydroxybenzyl)adipic acid monoethyl ester 3-(3-hydroxybenzyl)adipic acid monoethyl ester The corresponding diesters are prepared by esterification of these compounds with the selected alcohol by the usual method.

Those compounds having a benzyloxy substituent are reduced by the procedures of Methods A or C of Example II. Of course, the procedure of Example II, Methed A, results in hydrolysis of the ester groups and necessitates re-esterification.

EXAMPLE XXXII Alpha-hydroxybenzyladipic acid compounds corresponding to the products of Example XXXI are prepared by hydrogenation of corresponding benzoyladipic acid compounds according to the Method of Example XIV.

The a-hydroxybenzyl adipate diesters are further converted to the corresponding a-dimethylamino and a-monomethylamino derivatives via the tosylates by the procedure described in Example XIV. For this procedure hydroxy substituents other than the a-hydroxy group are avoided by employing the corresponding methyl ethers; likewise, amino substituents are employed in acetylated form.

The rx-amino benzyl adipates obtained in this manner are further converted to the corresponding 1-amino-4- tetralones of structure III by the procedures of Example VI.

EXAMPLE XXXIII The procedure of Example XXI is repeated to produce the following compounds from corresponding benzoyladipic acid compounds using lower alkylmagnesium halides.

diethyl 3-(a-hydroxy-a-phenethyl)adipate diethyl 3- zx-hydIOXY-a Z-ethyI-S-hydroxyphenyl] adipate dimethyl 3-[u-hydroxy-a-(Z-dimethylamino-S-methoxyphenyl ethyl] adip ate dimethyl 3-[u-hydroxy-u-(2-amino-5-methoxyphenyl) ethyl] adi pate dimethyl 3-[a-hydroxy-a-(2-acetarnido-5-methoxyphenyl) ethyl] adipate diethyl 3- a-hydroxy-a- 3-hydroxyphenyl ethyl] adipate diethyl 3- [a-hydroxy-a- 3-methyl-5-hydroxyphenyl) ethylJadipate diethyl 3-[u-hydroxy-a-(3,5-dimethoxyphenyl)etheyl] adipate diethyl 3-[a-hydroxy-u-(3-methoxyphenyl)propyl]adipate diethyl 3-[a-hydroxy-u-(2-chloro-5-methoxyphenyl) propyl] adipate diethyl 3-[a-hydroxy-a-(2-chloro-5-methoxyphenyl) butyl] adipate diethyl 3-[a-hydroxy-a-(3-methoxypheny1)ethyl]adipate In the above table, Me=CH Et=C H -Pr=C H Bz=benzyl. Ether substituents are converted to hydroxy groups by HBr cleavage; and acylarnido groups to amino groups by hydrolysis.

XXXVII 5-methoxy-8- chloro-33,10-trioxo-1,2,3,5l,4a,9,9a,l-

- octahydroanthracene Meihod A. A mixture of 10 g. of the ester product of Example XII, 250 ml. of glacial acetic acid, 125 ml. conc. HCl and 25 ml. of water is heated at 95 C. for 1 hour? During the first 45 minutes considerable effervescence occurs and the suspended matter gradually dissolves to give a deep red-brown solution. The reaction mixture is then poured into 2 liters of cold water and extracted with chloroform. The combined extracts are Washed with Water, decolorized with activated carbon, dried and evaporated to an orange-crystalline solid (6.9 g.) which melts at 171172-.8 C. After recrystallization from acetonehexane, the product melts at 172-173 C.

Method, B.The Z-carbobenzyloxy compound g.) corresponding to that of Example XII is treated with hydrogen gas at room temperature in acetic acid and in the presence of 0.5 g. of 5% palladium on carbon at 50 p.s.i.g. until one molar ecgiivalent of gas is taken up. The product is obtained by filtration and concentration of the reaction mixture after Warming to 60 C. for 20 minutes to ensure complete evolution of carbon dioxide.

Method C.--The product of Example XH (3 g.- is refluxed for 3 hours in ml. of acetic acid, 10 ml. of concentrated sulfuric acid and 1 ml. of water after which chloroform is added to the mixture which is then poured into excess water. The product is obtained by separation of the chloroform layer, washing, drying over sodium sulfate and concentration. A solid residue is obtained and recrystallizedfrom methanol.

desired, further purification is achieved by chromatography on silicic acid with chloroform elution. The product is contained in the less polar efiiuent fraction. e

EXAMPLE XPQCVI II The products of Example XXXVI are decarboxylated (benzyl esters by hydrogenolysis according to Method B, Example XXXVII and lower alkyl esters and nitriles by the procedure of Method Q, Example XXXVII) to produce the i'ollowing' compounds (Nitriles require a 24-hour reflux period):

X X1 X2 A H H 5-OMe 7 H 7-CF3 8-CF3 5-0M9 T H 7-EtCOz 8-Me H EtOOH(Me) 0 7-OBu 7 S-CF; B-OBu H i v-NHEt- S-OF; 5-OMe H 7-NHC0C3H1 H H i H 7-MeCOa ,8-01 5-OEt Et H ZZ8-CF3 H H s-01 5-OH H rI-Me 8-01 s-oH H 10 H s-NHMe 5-OPr H H 8-01 5-OBz H 7-Me S-Cl 5-OMe H 'I-NH; 801 513MB H 7-Et e01 5-0Me H H s-01 5-OMe Me H 8-01 5-OMe Et H 8-01 5-OMe Pr 7OMe 5-OMe H H 8-C1 5-OMe MBQCH: H s01 5-0H MeOCH(Me) 'I-Me e01 I 5-OH HOCH(C5H11) H 8-CF3 H Me H 8-01 5-OMe 7 V H H 5-OMe MeOCHz 7-Et H 5-0Me H H H 5-OEt Me 7'-NM82 8-01 5-OMe H 7-OMe 8-01 H 7-NHOOCH; 8-01 5-OMe H 7-NHCOC-Ha H 5-OH H 7-OH 8-01 e011 H 7-CF3 H 5-011 H 7-OBz H H Me 7-i-Pr 8-01 5-0H H i H S-CF; 5-OH H H H 5-Ome Me H H 5-0me H In the above table, 'Me -CH Et=C H Pr=C H- and Bz=benzyl.

Those compounds contaimng' bas1c(ammo) groups are isolated by acldificatlon with acetic ac1d 1n place of a mmeral ac1d. Armdes and esters are reacylated. t

7 EXAMPLE XXXIX Compounds of structure LX are oxidlzed using ozone according to the method of Example XXIX to obtain 40 acids of the formula: w t

? X1 A e /k COOH H X e X1 X: a A

H H H H H 7 ant 5-OMe H H 1 2-N 2 B-OMe H I H 2-NHCOMe 5-OMe H H 2-0Me H H H --2-Me 5-0H H 5-i-Pr 3-011 7. H 3- t 2-Et 5-611 H H H 3-OCH2C0H4 H H H B-EtCOa H g H H B-MeCO: H H H s-oH H s-NHcoMe H 3-OMe H 5-Et H 3-OMe H s-Me' H a-oMe H 5-NM62 H a-oH H B-Me 2-Me H H H1: 2-Pr 5-OPr H H H 3-0Me E1: H H 5 3-OMe Pr H H 3-OMe Me H Z-Me 5-OH H: 3-Me 2-Me 5-OH H 5 H H 3-011 Me H H s-oH i-Pr a-Me H 3-OH Ivie H H B-OMQ': H B-CFa H 3-OMe H 3-Me 2-Me 5-OMe H 5-MeCO; H 3-OMe H fi-NMez H 3-OMe H H H 3-0Pr Me H 20Me 5-OMe H 1 5-OMe 3-OMe H H Z-NMB: B-OMe H H Z-NEti 5-OMe H 5-Me H 3-OE1; H H H 3-0331: 1 H H 2-0Me 5-0CH2C5H5 H 

